StarCraft II's expansion pack, Heart of the Swarm, is already out in some parts of the world, and it's launching tomorrow in North America. To celebrate, let's take the opportunity to examine more than 20 years' worth of real-time strategy history in today's Show Us gallery, and see how much the genre has evolved visually. Since the StarCraft games are set in Earth's 25th century, we're focusing only on RTS games in sci-fi settings.